St. Louis: Geography and Climate

Located at the confluence of the Mississippi and Missouri rivers, St.
Louis is near the geographic center of the United States. Its modified
continental climate is characterized by four seasons without prolonged
periods of extreme heat or high humidity. Alternate invasions of moist air
from the Gulf of Mexico and cold air masses from Canada produce a variety
of weather conditions. Winters are brisk and seldom severe; annual
snowfall averages about eighteen inches. Hot days with temperatures of 100
degrees or higher occur on the average of five days per year. Severe
storms are often accompanied by hail and damaging winds, and tornadoes
have caused destruction and loss of life.